The present invention relates to a strip guide device, particularly for a cigarette manufacturing machine.
Cigarette manufacturing machines are known usually to comprise a feed unit inside which a paper strip, wound off a reel, is fed through a number of operating units on to a detour pulley about which the strip is wound and fed on to a horizontal bed. Between the said bed and the paper strip, there is located the top branch of a belt in the form of a loop and usually made of textile material permeable by air. In the proximity of the said detour pulley, the paper strip, moving along the horizontal bed together with the textile belt, is fed from above with a continuous stream of shredded tobacco from a feed device.
As it travels along the said bed, the paper strip is forced by the said belt to fold gradually crosswise, so as to form a continuous tobacco-filled cylinder generally referred to as a continuous cigarette rod, which is subsequently cut into single cigarette lengths.
In the event of the paper strip tearing upstream from the said detour pulley, during operation of the machine, a sensor, usually provided along the strip route, automatically shuts down the machine to enable the fault to be repaired by the operator.
Of the jobs the operator is required to perform for restarting the machine, one of the most complicated undoubtedly consists in rewinding the paper strip about the detour pulley and threading it through the extremely tight passage between the said bed and the end of the tobacco stream conveyor.
This operation, in itself difficult to perform on a single-rod cigarette manufacturing machine, is practically impossible on a dual-rod machine, i.e. designed to produce two parallel cigarette rods.
In the latter case, in fact, the paper strips are two in number and must be wound about respective pulleys coaxial with each other and located at the input end of the said rod forming bed. As a result, one of the said pulleys is concealed entirely by the other, thus preventing access by the operator.
In U.S. Pat. No. 4,336,813 filed by the present Applicant, G.D. S.p.A., insertion of the paper strips/s on to the rod forming bed is rendered automatic for overcoming the aforementioned drawback.
According to the said Patent, the cylindrical surface of the said detour pulley, which is located at the input end of the rod forming bed and constitutes a transmission member also for the said textile belt, is connected to a suction source.
According to the said Patent, the operator simply has to place the end of each paper strip on to the textile belt, at the point at which the said textile belt is wound about the detour pulley. When the machine is started up, the paper strip, held by suction on to the detour pulley, is fed by the same on to the said rod forming bed.
In actual practice, however, it has been found that, for the said operation to be performed successfully, and for feeding the strip correctly on to the rod forming bed, a sufficiently long portion of the strip must be arranged contacting the pulley, with the end of the strip already located on the horizontal rod forming bed. If not, when the machine is started up, the suction pulley fails to feed forward the strip, which is detached from the pulley due to the considerable drag created by means (transmission rollers and printing device) defining the strip route upstream from the pulley.
Consequently, when starting up the machine, especially each time the strip tears, the operator is required not only to arrange the end of the strip contacting the suction pulley, but also to insert the strip manually on to the bed through the said narrow passage.
This is obviously an extremely painstaking operation, especially on dual-rod cigarette manufacturing machines, on which one of the said two strips presents a route accessible only with difficulty by the operator.